A continual challenge in toner applications is maintaining a balance of print cost per page while maintaining print quality. Reduction of the toner particle size and adjustment of pigment loading is one approach to achieve this balance. However, the size of toner particles may only be reduced by so much while preserving proper function. Another way to accomplish this balance is to reduce raw material usage, which may be achieved, in part, through the use of porous toner particles.
Porous toner particles have been previously accessed in conventional milled toner particle systems by, for example, incorporating expendable water-soluble salt particles in a bulk composite composition prior to milling. In such a system, the additives are designed to be selectively solubilized after the product is milled to size. Such processes add manufacturing complexity because the additives generally require sufficient mixing operations to ensure even distribution of the additive throughout the resin matrix. Moreover, introducing these exogenous additives actually adds to raw material usage rather than reducing it.
Other processes to access porous toner particles have relied on complex multiple emulsion and suspension processes employing evaporative limited coalescence (ELC). Such processes are both material (solvent) and process time intensive. Moreover, such processes are generally complex requiring a careful balance of the miscibility of components between organic solvent(s) and water.